Psychoacoustics is a study of sound perception which shows that the human ear and the brain are involved in the signal processing of sound such that in various conditions, certain frequencies of the sound may be unheard.
Moving Picture Experts Group (MPEG) and other audio encoding technologies use these psychoacoustics principles to perform encoding and decoding of audio signals. For instance, high quality lossy audio signal compression may be achieved by identifying the parts of the audio signal that are unheard by the listener such that these parts may be allocated a lower priority in compression (e.g., may be lost in compression). Perpetual encoders utilized this fact to quantize or remove different frequencies so that they can compress an audio signal without introducing distortion. Additionally, the listener may not perceive the introduction of distortion in the audio signal during encoding. For example, it is well known that tones mask noise in an audio signal.